Cellulose propionate Preparation

Other mixed esters, eg, cellulose acetate valerate [55962-79-3] cellulose propionate valerate [67351-41-17, and cellulose butyrate valerate [53568-56-2] have been prepared by the conventional anhydride sulfuric acid methods (25). Cellulose acetate isobutyrate [67351-38-6] (44) and cellulose propionate isobutyrate [67351-40-0] (45) have been prepared with a 2inc chloride catalyst. Large amounts of catalyst and anhydride are required to provide a soluble product, and special methods of delayed anhydride addition are necessary to produce mixed esters containing the acetate moiety. Mixtures of sulfuric acid and perchloric acid are claimed to be effective catalysts for the preparation of cellulose acetate propionate in dichi oromethane solution at relatively low temperatures (46) however, such acid mixtures are considered too corrosive for large-scale productions. 

Cellulose esters (e.g., cellulose triacetate, cellulose diacetate, cellulose propionate, and cellulose butyrate) are prepared by initially treating cellulose with glacial acetic acid (or propionic acid and butyric acid) followed by the corresponding acid anhydride with a trace of strong acid as a catalyst in chlorinated hydrocarbon. Complete esterification reactions result in the formation of a triester, which undergoes water hydrolysis to form a diester. Cellulose acetate alone or in combination with cellulose triacetate or cellulose butyrate is used as a semipermeable membrane for osmotic pumping tablets, primarily in controlled release systems. The permeability of the membrane can be further modulated by adding water-soluble excipients to the cellulose esters. 

In the presence of water (moisture) the reverse reaction can occur and is indeed favored at ordinary conditions for organic acids. Consequently, cellulose esters from organic acids like acetic acid and higher homolog are prepared only by the removal of water as it is formed. The resulting product is moisture sensitive, the degree of which decreases with the progressive hydrocarbon nature of R. Therefore while cellulose acetate (R = -CH3) is susceptible to hydrolysis, cellulose propionate (R = -CHj-CHj-CHj) and cellulose butyrate [R = -(CHjlj-CHj] are hydrophobic, b. The formation of cellulose ethers, unlike that of cellulose esters, is not reversible. Cellulose ethers are therefore less sensitive to hydrolysis than cellulose esters. 

Esters of other aliphatic acids are prepared in a similar manner using the appropriate anhydride. Industrially important esters include cellulose propionate, cellulose butyrate, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB). The mixed esters, CAP and CAB, are prepared by using a mixture of anhydrides in the desired ratios, or by reacting cellulose with propionic or butyric acid and acetic anhydride. Both reactions require sulfuric acid as a catalyst. 

Historically, the first plastics were prepared by chemical modification of the natural macromolecular materials. Cellulosic plastics such as cellulose acetate, cellulose acetobutyrate, cellulose propionate, ethyl cellulose, viscose fibres and films are still used in the industry. 

Simple triesters such as cellulose formate [9036-95-7] (6), cellulose propionate [9004-48-2] (8,17), and cellulose butyrate [9015-12-7] (18) have been prepared and their properties studied none of these triesters is produced in large quantities. Cellulose formate esters, prepared by reaction of cellulose with formic acid, are thermally (19) and hydrolytically (6) unstable. Cellulose propionate and cellulose butyrate triesters are synthesized by methods similar to those used in the preparation of cellulose acetate with propionic or butyric anhydride in the presence of... 

CeUulosics [cellulose acetate, cellulose acetate butyrate (CAB), cellulose nitrate, cellulose propionate, ethyl cellulose] are ordinarily solvent cemented, unless they are to be bonded to dissimilar adherends, using conventional adhesives. In such cases, the following surface preparation method may be used. 

Cellulose Acetate, Propionate, and Butyrate. Cellulose acetate is prepared by hydrolyzing the triester to remove some of the acetyl groups the plastic-grade resin contains 38 to 40%... 

Cellulose esters of unsaturated acids, such as the acetate methacrylate, acetate maleate (34), and propionate crotonate (35), have been prepared. They are made by treating the hydrolyzed acetate or propionate with the corresponding acyl chloride in a pyridine solvent. Cellulose esters of unsaturated acids are cross-linkable by heat or uv light solvent-resistant films and coatings can be prepared from such esters. 

Amine-containing cellulose esters, eg, the acetate A/A/-diethylaminoacetate (36) and propionate morpholinobutyrate (35), are of interest because of their unique solubiHty in dilute acid. Such esters are prepared by the addition of the appropriate amine to the cellulose acrylate crotonate esters or by replacement of the chlorine on cellulose acrylate chloroacetate esters with amines. This type of ester has been suggested for use in controlled release, mmen-protected feed supplements for mminants (36,37). 

Desalination membranes with improved, rigid, and stable surfaces have been prepared from cellulose acetate propionate (170). These films are generally more resistant to hydrolysis than those from cellulose acetate. 

The primary OH group can be selectively blocked by the bulky triphenyl-methyl (trityl) moiety, followed by esterification at the secondary OH groups and removal of the protecting trityl group. Thus 2,3-di-O-acetyl cellulose has been obtained by this procedure. Moreover, regioselectively substituted mixed cellulose esters, acetate/propionate, were prepared by subsequent acy-... 

Systematic investigations were carried out for the preparation of cellulose acetate of D.S. 2,65 and other mixed esters which included cellulose acetate-propionate, cellulose acetate-butyrate, cellulose acetate-benzoate and cellulose acetate-methacrylate. The experimental conditions were optimised for maximum yield of the ester. Flat osmotic membranes were developed from these esters and characterised for their osmotic and transport properties. The nmmbra-nes were evaluated in a reverse osmosis laboratory test-cell using 5OOO ppm sodium chloride solution at 40 bars pressure. Table 1 presents the typical performance data of these membranes. 

Cellulose esters of the 2-.. 3-. and 4-carbon acids are readily prepared by the cellulose-anhydride reaction the acetate ester and the mixed acetate butyrate and acetate propionate esters arc manufactured and used in large amounts. Esters of higher acids require different synthesis techniques and tend to be prohibitively expensive except as specialty products. Some arc in commercial production, however. Cellulose acclalc phlhalatc, for example, is manufactured for use as an enteric coating on pills. 

Cellulose Acetate, Propionate, and Butyrate. Cellulose acetate is prepared by hydrolyzing the triester to remove some of the acetyl groups the plastic-grade resin contains 38-40% acetyl. The propionate and butyrate esters are made by substituting propionic acid and its anhydride (or butyric acid and its anhydride) for some of the acetic acid and acetic anhydride. Plastic grades of cellulose-acetate-propionate resin contain 39-47% propionyl and 2-9% acetyl cellulose-acetate-butyrate resins contain 26-39% butyryl and 12-15% acetyl. 

Materials. VEC was prepared by the catalyzed addition of CO2 to 3,4-epoxy-l-butene using conditions typical of that used industrially [77], then purified by vacuum distillation. Other raw materials were used as received without any additional purification. Mixed xylenes, vinyl acetate (VA), butyl acrylate (BA), butyl methacrylate (BMA), methyl methacrylate (MMA), styrene (St), and t-butyl hydroperoxide were obtained from Aldrich Chemical Company. Lupersol 575 (t-amyl peroxy (2-ethylhexanoate)) was supplied by Elf Atochem. Vazo 67 (2,2 -azobis(2-methylbutyronitrile)) was obtained from DuPont Chemical Company. Vinyl pivalate (NE05), vinyl 2-ethylhexanoate (V2EH), Tergitol NP-40 (non-ionic surfactant) and QP-300 (hydroxy ethyl cellulose) were obtained from Union Carbide Coq)oration. Aerosol OT-75 (surfactant) was obtained from Cytec. Sodium formaldehyde sulfoxylate was obtained from Henkel Corporation. Ethyl 3-ethoxy propionate (EEP), propylene glycol monomethyl ether (PM) and PM acetate (PM Ac) are Eastman Chemical Company products. 

This derivative is prepared by the reaction of cellulose with propionic anhydride and an acid catalyst under conditions similar to these for the cellulose acetates. As propionic anhydride is less reactive than acetic anhydride higher catalyst concentrations are used. See Table II for properties of cellulose triproprionate. 

Cellulose esters n. Any derivative of cellulose in which the free hydroxyl groups attached to the cellulose chain have been replaced wholly or in part by acidic groups, e.g., nitrate, acetate, propionate, butyrate, or stearate groups. Esterification is effected by the use of a mixture of an acid with its anhydride in the presence of a catalyst such as sulfuric acid. Mixed esters of cellulose, e.g., cellulose acetate butyrate, are prepared by using mixed acids and mixed anhydrides. 

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